Apparatus for producing indicia markings on work surfaces



1950 T. MILLER 2,517,502

APPARATUS FOR PRODUCING INDICIA MARKINGS ON WORK SURFACES Filed April 20, 1945 3 Sheets-Sheet l Aug. 1, 1950 MILLER 2,517,502

APPARATUS FOR PRODUCING INDICIA MARKINGS ON WORK SURFACES Filed April 20, 1945 5 Sheets-Sheet 2 Aug. 1, 1950 2,517,502

T. MILLER APPARATUS FOR PRODUCING INDICIA MARKINGS ON WORK SURFACES Filed April 20, 1945 ,5 Sheets-Sheet 3 Patented Aug. 1 1956 Theodoreitililler, Racine, Wis, assignor to George Gorton Machine Go Racine, Wis.-,--a corpora-- tionof Wisconsin application spiiiz'o, 1945i s'1erlai'nib': seine 1s- Glaims. (oite -i-s) ehisunvehtioaconcerns:apparatus-formation in g mdicia markin s on worksurfaces; a d the objects andnature ot 'the inv'ehtibn will b'ej made clear by thefollowing= explanationsofthe aocompanying drawings illustrating an example mechanicalexpressionorembo'diment of the inventionufrohi among other forms, modifications and embed withir-i -the spirit and scopeoi 'th'e iiiventi defined by the appended claims;

This application is a continuation." in part of the abandoned.applicati'cn nled'by me September 2 1942," Serial No: 457,088; for-Improvements in Apparatus for Producing Indicia ltl'arkings-v on Worse iv-races; a

To avoid distortion or" m'a- 'ng'l of Work sin faces adjacent to the letters or other identifica' 'tionmarks" punch-ed or stamped inoron the w'brk surface; and for' o'ther"reasonsit is now commen: practice to produce in or ori-metal work surfaces indicia markings by the electrioarc method. :By" this method; a vibrating consumable electrode is moved laterally over lthe 'work surface; and on each rapid short-amplitude oscillatory cycle I of -1 the electrode an electric arc is established andextinguished; bwmaking and breakingafi v electric iet'chingilcirouit thatin olude's the work'surface and the electrode: 'iihese electric arcspermanently m ark the metal work surfaces by the production therein or thereon of minute-pits orcraters that :do not distort the adjacent" portions of the metal surfaces, but merely burn-or vaporize themetal to forin such pits; Thecross" dimensions of these marking pits are substantially determined by the cross dimensions of the usually tenuous wire" lengths 1 composing the electrodes. Such electric arc etehers are usually carried by an etching head which can be carried or controlled in its lateral movements overthe metal Work surface by any suitable pantogra'ph mechanism having a stylus to trac'e a master pattern so that such pattern can. be reproduced; usually in s'caled 'relation on theiormation. or repr ochwtion of permanent inl 'dicia 'niarkings on- Work: surfaces; particularly work-surfaces that are not capable of being etchedorimarked-by th'ehereinbefore' described electric arc atchers;

A further'object -ot the-invention is the production of an etoh'er 'or rhairker' capable ofrapid 1y forming" permanentindicia markings in work surfaces by the use of rapidly oscill'atoryforciblystriking inipact: toolsor instruments capable of rapi'dly producing such worksurfa'ce a suece'ssion or'successioris of visible marking-"minute pits or craters" somewhat of-the' order of the marking pits or craters produced in themetal work surfaces :by said electric arcet'ch'ers'.

And-- another object" oi -the invention is" the pro=- duction of an etcher or marker foroperat-ion on workesurfiaces ccinprisinga head capable of-being carried laterally" over the Work surface, and supporting vibratory motor means; a percussive or impact tool hold'erral'pidly oscillated-by said motor means to forcibly strikethe tool against the work surface and retreiaitthe-tool therefrom during each" oscillationcycle; with the provision ofanie ans requiring the-tool to strike the work surtace 'With-the' desired markingforce during each:oscillatory'cycleof such-tool.

Anadditional object of theinve'ntion' is the provision of "means interchangeable with"- certain parts of the electric-aroetcher hereinbefore'described; cwliereby siicharc "etc-her, by cuttingv out or breaking the etching electric circuit thereof, can be icoiiverted into an? imp a'ct etcher or marker capableof producing lihdic-i'a markings on non cohducting-and other work'surfaoes.

A further object of the invention is to provide a v mechanical movement or amechanism which,

while particularly adapted for embodiment and use mend with an iimpactzetcher of theim en 'tio'n forteeding th'e tooliof th'e etcherto the work and/or for moving the tool= to and= from-the work surface witli the necessary work-surface marking force; is also of general utility to form xwhat may'be aptly termed Wdifier'ezitial ratchet" type or smech'arfical movement or mechanism for feedihgaunember or' element progressively in on-e vdirection"to a' predetermined or set limit ofmotion ih that direction; l .and/ or :forlmcving a mem bet 01 element in" opposite directions within predetermined or set and limits; and which-mecha-nical'emovement or mechanism of the inven tion :is characterize-d by the fact" thatit required-war forcedtooverhaut the member-or e1emerit" being'irhoved thereby? in both directions of motion?- withinthe predetermined or set end limits on rentals of motion;- but-in which a con.-

face.

3 siderably increased application of force is required to cause the mechanism to overhaul the member or element in one direction than the force required to be applied to cause the mechanism to overhaul the member or element in the opposite direction of motion.

With the foregoing .and other objects in view, my invention consists in certain novel and advantageous features, structures, combinations, and sub-combinations and arrangements as more fully hereinafter described, and as specified and defined in the hereinafter appearing claims.

Referring to the accompanying drawings, forming a part hereof:

Fig. 1 is a perspective of a head carryin an example embodiment of my instant invention for marking or etching work surfaces by the mechanical action of a rapidly oscillating impact tool, an example impact tool being somewhat diagrammatically indicated, with a portion of its oscillatory holder shown in position elevated from normal operative position with respect to the work surface to be operated on, said head being detached from the pantograph or other mechanism normally employed to carry said head laterally over the normally fixed work during the operation of reproducing indicia markings on the surface of such work.

Fig. 2 is an enlarged front elevation of the oscillatory tool holder and certain associated parts, located within the head of Fig. 1, (the cover plate of said head being removed and part of said head being broken away), certain parts being partially shown, the impact tool or instrument being diagrammatically shown exaggerated indimensions. 1

Fig. 3, is a more or less diagrammatical vertical section of the head of Fig. 1, taken approximately in the planes of the line 3-3, Fig. 2.

Fig. 4, is a more or less diagrammatical horizontal section taken approximately in the plane of the line 4-4, Fig. 2.

Fig. 5 is an enlarged detail vertical section of the insulating block or disk on the oscillatory member or arm that oscillates the tool holder,

the upper portion of the upstanding leverarm of the tool holder being shown in side elevation.

Fig. 6 is a more or less detail diagrammatical View of certain parts, showing in part any suitable circuit for operating the electromagnetic motor means.

Fig. '7, is a detail perspective somewhat diagrammatical view of the tool holder and certain associated parts, certain parts being partially broken away.

In illustrating an example embodiment of my instant invention, I happen to disclose certain operating and other parts of an electric arc etcher of a construction on the market and in commercial operation, without intending to so limit all features of my invention.

The instant etcher or marker comprises a suitable support that carries the working parts. If

so desired, this support can take the form of an attachment or accessory for a machine tool having a work table to which the work can be fixed, preferably, with its surface area to which the indicia markings are to be applied, in a horizontal position or plane. This machin tool usually provides a, cutter head, carrying a rotary cutter spindle and its cutter, operatively arranged above and perpendicular to the work sur- Such cutter head is usually universally movable laterally or in a horizontal plane over the work surface through the medium of a hand 4 operated and controlled pantograph mechanism having a stylus for tracing a fixedly located master pattern of the indicia design or markings to be reproduced on the work surface, usually in reduced scaled relation.

Where the etcher or marker is to be employed as an attachment for such machine tool, although I do not wish to so limit all features of my invention, said support can take the form of a head,

for example, a supporting box I, having a rigid upstanding stud-like shank 2, with certain parts of the work surface marking mechanism in said head, depending therefrom into operative position or relation with respect to the Work surface located below the head.

This Work surface marking accessory or attachment is operatively secured to the machine cutter head, after the cutter spindle has been temporarily removed therefrom, by inserting the shank 2, in the cutter head and rigidly and removably clamping the same thereto, preferably, with the longitudinal axis of the impact or percussion tool 3, of the marking head in alinement with the longitudinal axis of the machine cutter head.

In this particular example embodiment, the head I, is in the form of a supporting box or housing having an open side normally closed by a removable vertical cover plate 4, secured by suitable removable fastenings. This cover plate is formed at its lower portion with a. vertical slot ta, through which the lateral arm 5, of a suitable oscillatory tool holder projects to bring the tool 3, normally rigid with and depending from said arm, into operative relation to the work surface.

In this particular example, the oscillatory tool holder takes the form of a bell crank lever rotatably oscillatory on a transverse axial or fulcrum line "I, which in this example can be horizontal or parallel with the Work surface 11). This bell crank holder comprises the stiff lateral toolcarrying arm '5, and the stiff upstanding lever arm in, both rigid with respect to each other .and radiating from said fulcrum line substantially at The tool-carrying arm 5, is normally substantially parallel with the work surface, and the tool 3, is located on said arm at a point radially remote from said fulcrum line, and fixedly securedto the arm with the longitudinal axis of the tool perpendicular to the longitudinal axis of the arm, and also substantially perpendicular to the work surface. The tool depends from the arm toward said work surface, and substantially maintains its position perpendicular to said surface throughout its longitudinal oscillations in striking and retreating from said surface.

The tool 3, is preferably replaceably and removably fixed to its oscillatory holder in any suitable manner or by any suitable means. For example, the free end of the arm 5, of the tool holder is provided with a tubular socket 5a, extending transversely therethrough to longitudinally and slidably receive the upper end portion of the shank of the tool 3, and a radial headed clamping screw 5b, is provided for removably locking said tool in said socket against relative lateral and longitudinal movements with respect to arm 5.

The tool 3, is of any suitable structure, formation, and/or material that will satisfactorily perform the functions required; namely, by mechanical striking, impact, percussive or cutting action to produce in the work surface the desired permanent visible indicia markings, preferably, comarrest:

posed of minute crater-'ilikieipits xindenwtions, or

craters,v say, in diameter depth-substantially of the order of. thewpits or; craters produced bywth'e electric arc etchingimethod: l

The-tool 3, can'- consist f a straight'smallediameter wire-length, rod or shank- ;that .isstifi-or rigid against objectionable lateral-buckling; or defiection under the endwise impact blows to which itais subjected in action.

The lower or working. endof the impacttool 3,,

providesqa rigid strong longitudinal hard sharp or line puncturing-or indenting ,point 3a; that is in longitudinalalinement with the axis of tool 3. This-pointed working end 3a, of the toolacanbe formed by reducing the endofa hard steeltool i, to a longitudinally conical ortapered sharp point,

a or the working end of the tool-can berigidlygprosided with a diamond tapered to a longitudinal sharp point, or any other hardprecious sto "e or other suitable material can heari gidly secur.edi-to the tool 3, to form its working point.

These tools are particularly intended toinark work surfaces of electrical non-conducting mate' .rials, such as various hard plastics, hard lamilnated materials, glass, vitrified and enameled surraces, etc, although the invention is .not' so 16- mentioned example tool holder is rotatahlyo'scillatory, is established hy the longitudinal axis of-a cross head'BG, I, l, forminga rigid part of the holder Ill. This cros'sheadincludes the two "fixed stiff longitudinally alined opposite-end shafts .1, having. end heads. la, slid ably confinedlto parallel laterally-spaced fixed vertical guide rods 8, between which the cross head is arranged and by which the tool holder is confined against ohness, and is held to rotatable oscillationsin .a fixed plane perpendicular to the work surface. The end heads la; la, rigid with the alined 'end shafts 1', are preferably flattened"to-formone'an the guide rods 8', respectively, to facilitate assembl'y and disassembly of the holder and rods. (See Fig. "7,. in particular.) These end heads la, la, loosely embrace and straddle the guide'rods' "B,

that isyeach head "ia fits the respective guid'efro'd 3 on which it is received and mounted, with a slight clearance, so that, the heads 1a, 1a, are capa'ol e oflimi'te'd oscillation on and-relativeto-the rods- B, as the. holder rotatably oscillates on its axis L'T, he, with respect to said guide rods '8.

Any suitable vibratory motor means, can-"be "mouhtedln and carried by thehead- 'l, for rotatahly oscillating the" tool holder; 5, l0, 50, 611 "its transverse fulcrum line to rapidly strike the tool against the work surface-and lift the same therefrom on each oscillatory cycle;

In the instant example embodiment, I Show elect'rom'agnetic motor means for time oscill-at the'too'l holder, comprising an upright met tor block. l'l, fixed in the head I, behind-the oscill'atorytoolholder 5*, HI, andcarrying forwardly extending oore'l d-exposedatthe'elevated front oi the bloclgahdthe electromagnetic" coil ll, l'orxsaid .core, with :alternatingcurrent elechic powersourc'e Ma, for rapidly oscillatingthem'otor armature. In this particular examplaftlie motor armature l6; ll, is-arranged in operative relation to and. in front of the core and behind the tool holder 5,. l0, and is removably iflxed by, machine screws 2la, to the upper end: eta

iect'ionable relative lateral movements or loosenag,

eye and the other a fork to embrace. and straddle str'aightflatieiatively wide upstanding armature spring: a! hat itslowerend removably' ifixedtto and spaced forwardly from the iront lower portion of block d l by plates li and |-9,and.suitable removablewclamping meansv Ha, extending through said plateszand the upstanding springll and-into the block 41. i I 1 Thewarmature'16,21, is fixcd lto theotherwise freeupper end of the oscillatory spring H, which throughout-.itszoscillations canwbemaint ained substantially parallel with the corresponding-1y oscillating upstanding lever arm Ill, of the tool holder. Spring l l,-=in ;this-example, is located betweensaid holder arm 10,. andthe magnet core I5; and its motorbloclcll. Thefree upperend-otspring I], to which the armature t6, 2 I, is fixed, under, the influence of thee-magnetic.- iield when the power current isfiowing through thecoil :I-4,,rapid1y oscillates toward-and-from ithemagnet core l5, on preferably short amplitude oscillatory cycles of high frequency, say, oithe order or one hundred twenty per second, and having. an amplitude suitable .for worksurface marking. purposes, say, ofthe order of 315", although I do not wish to soilimit theinventi'on. I

The oscillatory armature LB, 2l', .is operatively coupled to the upper portion of the tool holder lever armin, by any suitable means to oscillate said iarm iri substantial synchronism With the spring 11, and consequently oscillate the tool holder on its transverse fulcrum axial line, to cariv the tool 3, longitudinally against andfrom the work surface while said tool maintained substantially perpendicular to said surface. .Forerample", the armature plate zl rovides :a rigid arm. or members, fixed thereto and extending horizontally andiorwardl'y therefrom in a plane substantially perpendicular to the plane of the armature-1 The member 9 projects forwardly beyond and intersects the longitudinal axial line of the tool-holder lever arm It, and this member 9 provides .a bore extending vertically therethrough'intermediate the length and width ofJmcmber '9, through which said arm l vertically extends, and by whichjit is confined to movefforwardly andrearwardly with the reciprocatlng oruoscill'ating member 91' With this example embodiment, the forwardly projecting metal member 3, is formed with an enlarged in- .te'rme'diateihole or opening extending vertically .therethrouehl and a relatively thick block or I92), of hard 'insulatingmaterial, is fixed on the .top of member '9 with a rigid central depending reduced nipple depending through and filling iaidcnlatgedwholeor opening through said mem- Therboreior holder lever arm l0, extends verticaHyand usuallycentrally throughsaid disk 9b, and its depending nipple in the hole or opening in member .9, and this hore has an internal-hiameter greater than the external diameter of holder arm .10, to thereby permit relative rocking movementsoflthearm l0- Within saidbore. In orderto provides metal bearing wear .and contacts'urface within saidbore for the arm lfl, a relatively-short metal bushing ,9a, is concentrically fixed in said bore, .in this instance, if so desired, in the lower end thereof, and this bush- Bahas an internaltdiameter greater than the external-diameter oithe holder arm ill. Inhthe specific example hereof, it so happens, that the loweruportionorlength of the bore through-the block or dislsSb is .formed of enlarged internal diameter to'receive'thebushing 9a, with the .bushhavlng an internal diameter substantially (see Fig.

cular bearing edge -90 provided by the bushing 9a. forms and constitutes the bearing surface of the member 9 that contacts the arm H] in order to confine said arm Hi to member 9, against objectionable looseness and possibility of chatter.

In the particular example illustrated, the tool holder 5, l0, and its attached parts, are suitably electrically insulated from the tool holder actuating member 9, and from the motor block H,

and the guide rods 8, fixed to motor block H by brackets l2, and from other parts that may be electrically included in the electric power circuit that actuates the electromagnetic motor.

In this particular embodiment of the invention, the electromagnetic vibratory motor, includes a longitudinally elongated armature spring ll fixed at its lower end and at its upper end fixedly carrying the armature from which member 9 projects forwardly substantially horizontally. Hence, the armature and member ll will oscillate in an arouate path from the center of oscillation located above the clamping plates securing the lowerend of spring H. For example, in this instance, this center of oscillation is located intermediatejand approximately midway between theupper' ends of the clamping plates l8, 19, which securethe lower end of the spring If to the motor block I l, and the lower end or side of the armature it, 2!, fixed on the spring 11. However, it to be understood that the particular "location of the center of oscillation of the armature and member 9, in this particular example of an'embodiment of my invention, is not a critical location for other embodiments, forms and. arrangements. This arcuate path of oscillation will dip or curve downwardly at the forwardportion thereof and thus cause the actuating arm or member 9 at the forward portion of its forward stroke to move down withrespect to the tool holder arm iii. In this particular embodiment, the vertical armature spring ll, when at rest; as when the electromagnetic motor is' not operatingfis not under tension but assumes its"normal straight, fiat vertical form holding armature l6, 2|, and hence the member -9 and the holder a'rm ill, at their respective positions of rest intermediate their respective end points of forward'and rearward oscillations. At its inactive position or po-.

is in this specific example, such that the distance of the rearward movement of the member 9- an d the parts associated therewith; isgreater than the distance of the forward movement thereof from their inactive positions or positions of rest,

although it is to be understood, that such condition is not essential to or a critical factor of my invention, as, if desired, for example; the dis- The arrangement'of the-spring ll with the armature I6, 2|, and-themotor core I5,

tance of the forward movement and thedis'tanceof the rear movement of the member 9 may be equal and the same, or, if the conditions of any particular embodiment or installation, such as the degree of flexibility or stiffness of the armature spring, make it of advantage or expedient, the distance of forward movement of the member 9 may be less than the distance of rear movement thereof.

The rotatably oscillatory tool holder organization, and its actuating member 9, as so far described, can be employed for electric arc etching where an etching circuit is provided, and on each oscillation the electrode merely more or less lightly touches or contacts the work surface to establish and then extinguish the work surface burning arc, as the mere slight contact between the electrode and work surface is solely for the purpose of establishing such work surface burning arc. A forceful blow of the electrode against the work surface is not only unnecessar but is ob- "9 and the electric arc etching electrode holder are operated at high speed with said holder under constant. gravity urge to bodily feed down toward the work surface with respect to actuating member 8. Under such conditions in arc etching, when the smooth surfaced holder arm [0, is oscillated at high speed by the actuating member 9, there results intermittent reduction of the frictional pressure between the smooth surface of arm l0, and the annular thinbearing surface 90, of the member 9, with bodil downward gravity feeding of the holder and its upright arm in through the member 9. This is satisfactory for electric arc etching but not for mechanical impact tool etching.

I have discovered that if a proper impact marking tool is substituted in the arm 5, of the oscillatory holder 5, ID, for the electrode carried by such holder for are etching, and if added features are cooperatively associated with both the lever arm Ill and the actuating member 9, to resist upward movements longitudinally of arm [0, between member 9 and arm 10, during each stroke of holder arm 5, and its tool 3, toward and against the work surface, the tool will strike the work surface under sumcient force and pressure to successfully carry on mechanical impact marking of such work surfaces when of non-electrical conducting and certain other materials. My instant invention contemplates the use of any suitable means that, while permitting rela- -.tive longitudinal movement of the oscillatory holder arm I0 relative to its actuating member 9 away from and toward the work surface, will automatically cause greater resistance to be olfered to such movement of the holder arm It away from -.the=WO1k surface, than will be offered to movement of the holder arm l0 relative to the actuating member 9 in the opposite or reverse direction, that'is, toward the work surface, during each tool holder oscillation from and toward the work surface. In other words, the means contemplated and provided by my invention for associating the oscillatory holder arm ID with the actuating member 9 for oscillating the same, is such as will permit movements of the holder arm I0 and itsactuating member '9 relative to each other, but will require the application of a greater force to cause longitudinal movement, of arm H] relative to actuating member vll away from the work surface. than the force required to be applied to cause movement of the arm Hi relative to the member 9 toward the work surface. Thus, an operative association of the actuating arm or members. and the tool holder arm H3 is providedlby which memher 9 and arm ID are movablerelative to each other, but in which resistance is ofiered to such movements. The magnitude of such resistance is, as explained above,suchthat greater resistance is offered'to movement of the tool holder armlfl away from thework than is offered to movement thereof toward the work. In this manner an amount of kinetic energy from the total kinetic energy stored in the armature spring system, is transmitted to the tool holder arm [0 during oscillationof the tool holder toward the worksurface, and henceythe required amountoflsinetic energy to be transmitted to the tool holder arm l0 during oscillation of the tool holder toward the work surface, necessary to force tool 3-to strike the worksurfaceduring such oscillation with sufficient force or impact to cause the mechanical impact marking of such surface, can be determined by providing a resistance to movement of the tool holder arm ill away from the work surface, of a required predetermined magnitude.

, For instance, various camming means canbe cooperatively associated with the tool-holder arm l0 and the actuating member Bufor such arm, to successfully solve the above mentioned problem and attain the desired results; A's-one example embodiment fromwamongother camming means that can be employed, I provide the upstanding lever arm It, with a longitudinal smooth fiat wedging or camming surface a, the exterior smooth surface of the arm It being otherwise preferably cylindrical. This surface (1, extends longitudinally throughout and beyond that portion of the length of arm Ill, that passes through the member 9, orthat willtbe locatedin said memher during the marking operations. This fiat'a, takes the form of a plane arranged longitudinally of arm In, and intersecting the same at a wedging or'camming angle to the longitudinal axis thereof. Thus, the wedging fiata is inclined from a lower intermediate surfacepoint in the length of arm: ill, and extends longitudinally and'in-wardly thereof toward its longitudinal axis to itsupper end... This flatva, is preferably located at'the front side of the arm lil, that is, the advancing side of said arm when said. arm and thetool holder are moved forwardly to strike the tool on the work surface. The straight, fiat, inclinedpl'ane surface a, longitudinally increases in depth toward the upper or top end of arm H3, and thereby coopera-ting force applied radially of said arm 1:9. from the arm 9, against. said cam surface a, resists longitudinal upward relative movement, of said arm l9, under certain conditions, with'respect to the actuatingmember 9, until such. resistance is overcome by the application of an opposing force of sufiicient magnitude. applied radially of said arm it from the actuating member 9, against cam surfaced, is preferably of sulficient magnitude to prevent the arm in from moving or feeding. longitudinall downwardly under the force of gravity acting thereon, while the actuating member 9 and the arm it carried thereby are at rest,due-to frictional forces which-are established-acting. on the arm II} to re- The cooperating force I sist' :andovercome thegravity urge thereon, but due 'to the formationand arrangement of the flat, inclined: plane surface a, the force required to be appliedto relatively longitudinally move the tool holder arm l-ll' relative to actuating member .9 toward the work-surface, is considerably less than the :forc re uiredto be applied. to move holder arm. :10 intheiopposite direction, that in a directionaway from the work surface.

In this particular example, said radial fore ca-rrie'd byvthe actuated member 9 is slideably appliedntogthe inclined-cam surface a, through the medium of -.a ;longitudinally slideable springpressed plungenb, arranged radially of the tool holder arm til-,-and carried.- by the block or disk lli-rigid-w' h-actuating arm 9; and longitudinally slideable through said block, and preferably providedwith-a smoothor rounded inner contact end constantly held under spring pressure in camming, slidingfandfrictional engagement with the longitudinally inclined cam surface a of arm'dfl.

'lIhe plunger 17, is preferably longitudinally slideablein and confined by afixed bushing c, extendingra'diallythrough-the block 9b, from the vertical bore thereof to a point at the exterior of saidblock. This radial plunger is preferably located ina horizontal plane above the horizontal plane of theannular bearing edge 90 that contacts holder arm I50.

Any-suitable spring: -m'eans can be provided to constantly maintain the longitudinally slideable plunger under therequired yielding inward pressure-against thecam surface a, of holder arm in. For-example, from among other spring means that ean 'be employed, 1 show spring d, exteriorly coiled-around block so and atoneend fixed theretowithits active free end-d, under constant tension(tospringinwardly toward the block surface. Iihis active sprin end d traverses the outer end of plunger b, l-te constantly tend to force said plungerinwardly' against cam surface a. The projecting outer end of bushing 0, can be slotted to guidetand maintain. spring end d in constant operativeacontact-with the outer-end of the plunger. The-plunger -b,, is. located in the vertical plane that includes-the longitudinal axis of holder arm it, whichfis alsoethe vertical plane in which said arm It, oscillates-forwardly and rearwardly. As the longitudinal cam surface a, of the holder armldislocatedat the front oradvancing side of holder arm it, when the holder is on its forward. oscillationcarrying the tool 3 down to strike thewor'k surface-the rear-wardly, spring pressed plun er his alsoclooated insaid front side of arm 4n exerting rearward pressure against cam surface a, of said arm.

The relative arrangement of the arm [0, and its longitudinal cam surface a, with respect to the transversely"oscillating actuating arm or member 9and its plunger hare such that during tool holder oscillation, the holder arm [0, is under the constantradially applied forces exerted thereon by theplunger b to establish friction forces between the surfacesc of the actuating arm or member 9 and the inner end "of the plunger 1) and adjacent cylindrical or curved surface of the holder arm "H3, and between the inner end of the plunger b andthe inclined fiat surface a of arm it, so that, upward longitudinal movement of arm H3 is resisted to a greater degree than downward longitudinal movement thereof, through and with respect tothe actuating arm or member 9.

Assuming that the motor is at rest with the spring H and its armature and the tool holder and its tool 3, in the positions as shown in Figs. 3 and 6, then, upon energizing the motor, the armature l S is pulled rearwardly toward the core I5 with relatively great acceleration and due to the inertia in the tool holder, the bushing 9a and member 9 slip upwardly a short distance on or overhaul arm Ill, that is, in effect, the arm I!) slips downwardly a short distance relatively to the bushing 9a and the actuating arm or member 9, before the tool holder can be accelerated to the speed of upward and rearward movement of the bushing 9a and the actuation arm or member 9. However, as soon as the tool holder has attained the speed of movement of the bushing 9a of actuating arm 9 as such arm and the bushing move through their upward and rearward path of oscillation, the holder arm Ill is picked up by and proceeds at the same rate of movement as and moves upwardly and rearwardly with, actuating arm or member 9. At the same time the end heads la, la, of the shafts I of the tool holder, are moved vertically on rods 8, respectively, and the point 3a of the tool 3 has the resulting compound motion applied thereto so that the tool point 3a partakes of such motion.

' When the actuating arm or member 9, and the tool holder including the tool holder arm l and tool 3,.have reached the end limit of their rearward oscillation or movement, the tool holder and tool 3 are at their limit of upward and rearward movement, and core I5 is deenergized and the deflected armature spring" is released, so that, the energy stored therein will oscillate or spring the spring and the armature forwardly away from the core l5, thus reversing the direction of movement of the armature and of the member 9 and tool holder associated therewith. Upon the reversal of the direction of motion of the armature, by the spring [1, as aforesaid, the member 9 and the tool holder arm [0 and tool holder 5, are accelerated in a direction forwardly and downwardly from their respective end limits of upward and rearward movement, by the armature spring. And again the inertia of the tool holder arm I I! and the tool holder carried thereby, functions to cause the bushing 9a of the actuating arm or member 9 to slip downwardly on and overhaul the holder arm lll, the holder arm ID in effect slipping upwardly through the bushing 9a, but while the inertia of the tool holder assembly is the same on this forward stroke as on a rearward stroke, nevertheless, the bushing 9a and actuating arm or member 9 will slip downwardly on or overhaulthe arm ill for a lesser distance or extent than the distance that the bushing 9a and arm 9 slips upwardly on and overhauls arm ID on the rearward stroke or oscillation.

This difference between the distance the bushing 9a and arm slip upwardly on Or overhaul holder arm ill on the rearward and upward oscillation stroke and the distance which the bushing 9a and arm 9 slip downward y on or overhaul the arm ID on the forward and downward oscillation stroke, notwithstanding the fact that the inertia of arm H) and its associated tool holder is the same on both forward and rearward oscillation stroke, is due to the fact that the arrangement of the inclined surface or flat a and the presser fpin b which engages such surface, is such, that the pressure exerted by presser pin b upon the inclined surface a of arm [0 requires a greater force to move arm 9 and bushing 9a downwardly on and relative to arm in than is required to move the bushing 9a and arm 9 upwardly relative to'the arm In. As the armature IS, with the tool holder actuating arm or member 9 and tool holder assembly carried thereby, move forwardly and downwardly through the forward oscillation stroke, the end heads la, la, of the tool holder shafts 7, are also simultaneously moved downwardly on the rods 8, respectively, and the tool point So of the tool 3 carried by the tool holder again has the compound motion imparted thereto, so that the tool point 3a partakes of such compound motion.

Thus, a yielding association or junction is provided between the holder arm El and the bushing 9a in which said arm is received and mounted on the actuating arm or member 9, of a character to permit upward motion of the arm ill through and relative to the bushing 9a while the actuating arm or member 9 is still in its forward and downward oscillation for impact striking of the tool 3 on the work surface 2. With the yielding junction between the arm Ill and the bushing So, if the arm Hi has on the rearward oscillation stroke of the actuating arm or member 9, dropped downwardly a distance greater than the distance necessary in order to compensate for wear of the tool point 3a or for undulations in the work surface, then, of course, the tool point 3a will on its forward oscillation stroke contact the work surface before the member 9 has completed its forward stroke. Under these conditions the up wardly acting forces imposed on the arm It by this premature engagement of the tool point 3a with the work surface, will overcome the forces acting on the arm H] to resist upward movement thereof through and relative to bushing 9a and to the actuating arm 9, so that arm [0 will be forced longitudinally upwardly through bushing 9a the required distance to permit actuating arm 9 to complete its forward oscillation.

But while this junction between the arm ill and the bushing 9a must be yielding, it must also be capable of transmitting the'desired amount of kinetic energy from the armature spring sys-- tem to the tool holder, and the amount of energy so transmitted is primaril dependent upon the pressure exerted on the inclined plane or flat 0. by the presser pin b, and the inclination of the inclined plane or flat a relative to the longitudinal aXis of arm 10, and the coeflicient of friction between the coacting parts. The cooperating action of the camming device consisting of the fiat inclined surface a on the arm in and the presser pin b carried by the bushing 9b, during operation of the oscillatin or actuating arm or member 9, while the tool holder assembly is thereby oscillated on and about its fulcrum line I, automatically, in effect yieldingly locks or maintains the tool holder arm I 8, against upward longitudinal movement through the bushing 9b on the oscillating actuating arm or member 9, during each forward stroke of the tool holder that carries the tool point 30 of the tool 3 into strikinng contact with the work surface. Each surface striking stroke of the tool 3, is hence, forcibly made under the required downward pressure or force to mechanically produce the desired mark by impact or percussive action on the work surface.

By varying the tension of spring d and consequently the lateral camming or wedging pressure applied to the longitudinal upwardly and rear wardly inclined plane cam surface a of the tool holder lever arm l0, through the medium of the Spring pressed plunger b, and by varying the angular relationship between the inclined cam memos" surface I c, and the-longitudinalaxis oti'itlie' lever arm 1-0, the: downward pressure, or downwardly acting force, :on,.- and hence the striking: force of; the tool :3, on the work surface-may Ive-varied .over

awid'e range within the limits -of' the particular organization. I v l .In the particular. example illustrated the oscillatory: tool holder .5, till zands--its tool :37; are: nor

mally held in an elevated'inoperativeposition with. respect to: the work surface :w,gbytany:-suit-- able forwardly spring pressed plunger-r 25, having a radially projecting lifting toeslib located below. a lifting arm .26, rigid with the .tool holder lever arm Ill and projecting therefromwintor the path of vertical movement of the toe 25b; The spring elevated plungerizfi (see Fig. 1) constantly :tends to raise holder: :5, Hli' withrrespect to a'Q-i tuating arm 9, and guides 'l, and to 'main'tainsaid' holder. in elevated position. inoperative relation to the work surface. Whennit is desired to produce 'indicia marlr ingonthe work suriace.

the power circuit is closed through. the elect-Iomagnetic motor to start the tool'l'holder oscillation; and thereupon themachineioperatorfby"ape plication of downward pressure on the: exposed: head or' button 25a of plunger: 25;.. torcesssaid plunger to its limits of downward movement against the'cupward pressure of it'siili-fting spring 28', and thereby permits the-thenoscillating-tool holder til to be: progressively fed downwardly: until stopped by" the engagement/lot tool: 3 the work surface This progressive downward feeding of the tool holder results from the iact" that on each rearward and upward stroke or oscillation of the actuating arm .9', such .actuata position where it thencontinues tdrotatabIyand vertically oscillate relativeto the work sur'- face to with the point 311 of the tool 3' rapidly successively striking the work surface 'withlsui ficient'iorce or impact to form the desired markings on the work surfacepas the :tool. is gmotionedlaterally relative to the work surface. As above explained, the tool holder. andi'tlie tool 3 are under constant urge. toward.the'worksurface, so thatgtool point wearorundulations of the work surface will be automatically.compensated for as a result of the relative arrangement and assowr ciation between the tool holder. arm 110 and the bushing 9a carried by the oscillating actuating arm 9, through the medium .of -the camming means'provided by the inclined flatcam surface a on the arm iii engaged by thespring loaded.-

presser pin 1). v

Thus, during a normal.markingoperation, the operator holdsthe plunger 25 depressed, butas. thisplunger 25 is underconstantspring pressure to return to elevatedposition, whenthe operator; completes the marking operation, the head. or

. button 25 may be released and the lifting device will thereupon immediately lift the holder 5,10 from operative position. However, it is not deemed. necessary to .fully illustratethis lifting deviceherein, as it, forms no part of.my .invention, and I do not wish to limit my invention to inclusion therein or use therewith.

Fig. 12- lof the dates, 1 happcn cashew-- verticalnsmooth wirelengths "23; depending in front of. the cylindrical end shafts l, andnconstantly exercising more .or less-rearward. lateral. pressure against said shafts 1, to yieldingly' hold the shaft 61141515! laterally against the guidesrfl, respectively, so as to. avoid chatter whenthe-tool holdenisoperating at high speed; These spring lengths 23flcan ibe securedat their upper: ends with the rearwardly' pressing lower. ends iree'rand slideabl-y engaging :the shafts 1;, respectively.

However; my instant invention is not limited to" theemployment of such lateral pressure means as such means are not essential 01: necessary. For example; IJhave discovered that when the springtd exerts a force of'su-ihcient magnitude-to engage the pin '1) under a considerable pressure against the cam surface a of the tool holder arml'll, that the springwirelengths or. fingers '2 3 need e used and are not necessary in order to prevent chatter;

Whi'lethe' rerce excrtedribythe spring wee lengths or 5 fingers 23, when such. fingers are ar ranged as disclosed in the exampleherein-illustrated-is applied primarily for the. purpose-of preventing lateral motion of theishaftlends 1a relative to the rods 8 on which they are mounted, so'a's to prevent chatter; attention is directed. to the fact that my invention. contemplates and inclu'des the use of these fingers 2t to'zapplydowm" ward acting forces'to the tool holder, :thatis, in

a direction toward the worlcsurface; :Such com templated function for the fingers 23 is eaoc1o1nplishe'cl in the present instance thy inclining the" -upper end lengths of the fingers 2.3 rearwardlyr above fshafts 11, "relative. to the vertical. plane traversed "by these shafts so that; these spring fingers then yieldingl y press downwardly upon shafts L'as-will be readily understood. I

"In the particular example illustrated, without intending to submit my instantinvention, the tool-"holder is' confined and guided to straight-line bodily vertical movements "by smooth surface de-- pendin rods a; rigid with and-depending from brackets l2 projecting forwardly from the motor block H; and rcmovably clamped thereto byremovable machine screws IZ'a' or other suitable means, for ease in assembly and disassembly; Ajlso if so. desired, the. lower end or one .or both 'iof sai'd guides .8, can be provided with a .r'emov able 'stoptcg'for ease in removing and applying theftoolhoder to and from said guidesfi,

f is hereinbeforestated, it is desirable to electrically insulate; the tooLholder andits impact 12691.6, fromthe power. circuit that oneratesithe' electromagnetic vibratory motor. Hence; should itlbe. desirable to, form the block 9?), onthe vibratory hQIderactuating arm 9, of metal or electrical conducting material, the holder lever arm ID,

' canbe composed .of two axially alinedmetal rods.

insulated jfrom each other and rigidly connected bya ooupling,,.composed of insulating material a and an, exterior' rigid tube or sheathing- 'Iihe'tool holder can also be insulated from" the brackets l2, and guide rods 8, by insulationm,

(see'Fig; 'lljbetween each shaft TI; and the cross head .50,

composed of a single rod .as'jshown by'Fig. 6.: l;l'owever, I do not intend or 'wish to limitmy insltantihventi'on to such specific examples.

it"i'sal'so" a further-purpose or this embodl-- ment to permit replacement of the etching electrode by a mechanical etching or engraving tool, such as a diamond of conical shape supported in a suitable shank or other holding means so'that indicia or the like may be mechanically inscribed on non-metallic surfaces as glass, plastics, and the like, by means of the short percussion blows of the engraving tool on said surfaces, and without the aid of electric arcs.

Although I do not wish to so limit all features of my instant invention, the specific embodiment shown herein as an example was particularly designed as an interchangeable accessory, applicable to and removable from, a known commercial type of electric arc etcher, to temporarily or otherwise, convert the same for use in producing indicia markings on work surfaces of nonelectrical conducting materials by a mechanical impact tool or the like. Obviously, however, my instant invention can be employed in more or less permanent form as a complete machine for producing indicia markings on work surfaces by the mechanical action of any suitable impact or striking tool or instrument.

The instant disclosure shows the example embodiment of my invention included in said commercial electric arc etcher, in place of the electrode holder, the electrode, the etching electrical circuit, and the insulating plug forming the bore of the motor driven oscillatory arm that actuates the electrode holder of said are etcher.

For instance, the tool holder 5, l0, can be removed by dropping the same down through the block 9b until the eyes 1a are clear of the rods 8, the stop 8a having been removed, or the rods 8, can'be detached by removing the screws in that secure the brackets l2, to the motor block and then the arm 9, can be removed with the tool holder and its lever arm H) by removing the screws 21a. securing armature block 2| of the armature 2!, l6, and its spring can be removed with the tool holder 5, I!) by removing the screws Ha that secure the spring clamping block l8.

By my invention a mechanical movement or mechanism is provided for moving or progressively feeding a member or element in one direction to a predetermined limit of motion for the element or member in that direction, and/or for moving a member or element in opposite directions within predetermined or set end limits. A mechanical movement or mechanism of the invention may be aptly termed a differential ratchet mechanism, the term ratchet being used in abroad, generic sense for purposes of convenienceprimarily, and not in its more limited mechanical or specific structural sense. The mechanism functions as a ratchet," in that, it overhauls the member or element to be moved for a distance before engaging and moving the same in either direction of motion of the member, but is so arranged as to overhaul the member a greater distance in one direction of motion than in the other or opposite direction of motion, with the result that, the element is progressively fedin only one direction of motion. The adaptation or mechanical expression of this mechanical movement of my present invention, as disclosed and described herein, is, of course, primarily adapted for moving or vibrating the impact tool of an impact etcher toward and from the work surface, but it embodies the principles of this mechanical movement of my invention in that, the member In which forms the carrying arm for the tool holder is so cooperatively associated withthe oscillating actuating member 9, through the medium of the camming means consisting of the camsurface a on member ID engaged by the pressure'ipin b on member 9, that, as the actuating member. 9 is oscillated or reciprocated generally' longitudinally of the member ID, it will overhaul or slip along member [0 for a distance during. its movement in either direction, due to inertia-forces, before frictionally holding and moving the member, but will overhaul member I!) a greater distance in one direction of motion than in the other, with the result that, while the member I0 is alternately moved in opposite directions, that is, oscillated through a fixed path, it will be progressively fed or moved step by step in the direction of motion opposite to that direction of motion or stroke of member 9 during which member .9' overhauls the member ID for the greater distance.

This -.differential ratchet mechanical movement or mechanism of my present invention is adapted to embodiment in various arrangement and combinations to meet particular operating and useconditions, such for example, as a mechanical-:movement or mechanism for limiting pressure in rectilinear motions.

The disclosures hereof have been specifically described merely for purposes of explanation and not for'purposes of limitation beyond that required. by the appended claims, as I realized, as will be evident, that various modifications, variations, "changes, adaptation, substitutions and eliminations are possible within the spirit and scope of my invention.

What I claim is:

1. Apparatus for producing permanent indicia markings on work surfaces by the mechanical actionoffa'n impact marking instrument; comprising a holder for the impact marking instru-- menty said-holder adapted to fixedly hold said instrument substantially perpendicular to the work surface, said holder being oscillatory to carry said instrument endwise into forceful marking engagement with said surface and to lift said instrument therefrom on each oscillation cycle; vibratory motor means for oscillating said holder'including a holder actuating connection, said holder being relatively movable with respect to said'connection; and wedging means between said connection and said holder for exerting wedging ur e on said holder and said instrument toward "the work surface during each surface striking stroke of said instrument to resist relative upward movement of said holder with respect to'saidconnection under the impact of the instrument on the work surface.

2. Apparatus for producing indicia markings on a worksurface, comprising a holder; an inrpact surfacemarking tool normally rigidly fixed to said holder and depending therefrom toward the work'*surface substantially perpendicular to said surface, said holder being oscillatory to forcibly endwise strike said tool against said sur-- face and raise the same therefrom on each oscillation cycle; means for oscillating said holder including an oscillatory motor and a holder actu ating member oscillatory in a fixed path transversely with respect to the axis of said tool driven by said 'motor, said holder being relatively rockable and transversely movable with respect to said member during said oscillations; and camming means between said holder and said member.

3. Apparatus for producing indicia markings on a work surface, comprising a holder; a mechanical work surface marking tool normally 17 rigidly held by said holder for endwise forcefully striking the work surface; said holder being oscillatory to forcefully strike said tool against said surface and lift the same therefrom on each oscillatory cycle; an oscillatory motor operatively and slideably coupled to said holder to oscillate the same and permit relative movements thereof toward and from said surface; and camining means acting on said holder to resist movement of said holder and its tool longitudinally away from said surface during each surface striking stroke of said tool.

l. Apparatus for producing indicia markings on a work surface, comprising a holder; a mechanical work surface marking tool normally rigidly held by said holder for endwise forcefully striking the work surface; said holder being os cillatory to forcefully strike said tool against said surface and lift the same therefrom on each oscillatory cycle; an oscillatory motor; a coupling operatively slideably coupling the motor with the holder for relatively moving the holder toward and from the work surface; camming means acting on said holder to resist movement of said holder and its tool longitudinally from said surface during each surface striking stroke of said tool, said camming means including a longitudinally inclined camming or wedging sur face on said holder, and means on said coupling for applying pressure on and transversely of said wedging surface, said cannning means being actuated to exert force on the holder to re'ist movement of the tool holder and its tool longitudinally away from the work surface with respect to said coupling under the impact of the tool against the work surface.

5. Apparatus for producing indicia markings on a work surface, comprising a holder; a mechanical work surface marking tool normally rigidly held by said holder for endwise forcefully striking the work surface; said holder being cs cillatory to forcefully strike said tool against said surface and lift the same therefrom on each oscillatory cycle; an oscillatory motor; a coupling operatively slidably coupling the motor with the holder for relatively moving the holder toward and from the work surface; camming means acting on said holder to resist movement of said holder and its tool longitudinally away from said surface during each surface striking stroke of said tool, said cainming means including a longitudinallyelongated laterally inclined cam flat or surface provided by said holder, and a spring pressed plunger supported independently of holder and cooperating with said surface to tablish forces to resist movement of said holder in a direction away from said work surface.

6. Apparatus for producing indicia markings on a work surface, comprising a holder; a mechanical work surface marking tool normally rigidly held by said holder forendwise forcefully striking the work surface; said holder being os 'cillatory to forcefully strike said tool against surface and lift the same therefrom on oscillatory cycle; an oscillatory rnotor; couplz' means operatively slideably associating the motor with the holder for relatively moving the he and its surface marking tool toward and. from work surface; said surface marking tool being stiff against lateral deflection and depending from said holder toward the work surface and being provided with an axially alined hard sharp surface indenting point; said holder including a longitudinally movable lever arm; and said coupling means providing a holder oscillating mem 18 ber vibratory transversely of said arm with said arm operatively confined thereto for relative sliding movements with respect to said member.

'1. Apparatus for producing indicia markings on a work surface, comprising a holder; a mechanical work surface marking tool normally rigidly held by said holder for endwise forcefully striking the work surface; said holder being oscillatory to forcefully strike said tool against said surface and lift the same therefrom on each oscillatory cycle; an oscillatory motor; coupling means operatively connectin the motor with the holder for relatively moving the holder and its tool toward and from the work surface; camming means acting on said holder to resist movement of said holder and its tool longitudinally away from said surface during each surface striking stroke of said tool; said coupling means providing for movements of said holder vertically in opposite directions relative to said coupling means; and said camming means acting on said holder to resist movement of said holder and its tool longitudinally from said work surrace.

8. Apparatus for producing indicia markings on a work surface, comprising a tool holder rotatably oscillatory on a transverse axis; an impact work surface indenting tool normally fixed to a holder to forcefully strike the work surface and withdraw therefrom during each oscillation cycle of the holder; a holder actuating member oscillating'in a f xed path; a vibratory motor for oscillating said member, said holder being coupled to said member in driven relation, said holder being vertically movable with respect to said member during holder oscillations; and means for applying wedging pressure on said holder to resist upward mover'nentof the tool during each stroke of the holder to forcefully strike the tool against the work surface, said means including an upwardly and laterally inclined longitudinal wedging surface provided by the holder, and a plunger carried by said member substantially perpendicular to said wedging surface and spring pressed against said wedging surface. I

9. An accessory comprising an oscillatory tool holder having a, work surface impact or indenting tool normally fixedly secured thereto, said holder including an actuating lever arm provided with a longitudinal laterally inclined cam or 'wedging surface; and an actuating member for oscillating said holder, said arm transversely traversing saidmember for relative longitudinal movements with respectwthereto and provided with a plunger spring-pressed against said cam surface to exert wedging urge against said lever arm.

10. Apparatus for producing indicia markings on a work surface by the mechanical action of an impact marking tool; comprising a holder for the impact marking tool, said holder being adapted to fixedly hold said tool substantially perpendicular to the work surface, said holder being mounted for oscillation to carry said tool endwise into forceful marking engagement with said surface and to lift said tool therefrom on each oscillation cycle; means for oscillating said holder; an actuating member operatively connectin said holder with said oscillation means, said holder being relatively movable with respect to said actuating member toward and from the work surface; means engaging said holder adapted to resist movements of the holder in either direction; and said holder and holder 19 engaging means being constructed and arranged to offer greater resistance to movement of the holder in a direction toward the work surface than to movement of the holder in a direction away from the work surface.

11. Apparatus for producing indicia markings on a work surface by the mechanical action of an impact marking tool, comprising a holder for the impact marking tool, said holder being adapted to fixedly hold said tool substantially perpendicular to the work surface, said holder being mounted for oscillation to carry said tool endwise into forceful marking engagement with said surface and to lift said tool therefrom on each oscillation cycle; means for oscillating said holder; ,an actuating member operatively connecting said holder with said oscillation means and being adapted to be oscillated by said means to oscillate said holder; said holder being slidably engaged with said oscillatory actuating member and being relatively movable with respect to said actuating member toward and from the work surface; and means constructed and arranged to engage said holder to establish friction forces between said holder and said actuating member acting to establish greater resistance to movements of said holder away from the work surface than to movements of said holder toward the work surface.

12. Apparatus for producing indicia markings on a work surface by the mechanical action of an impact marking tool, comprising a holder for the impact marking tool, said holder being adapted to fixedly hold said tool substantially perpendicular to the work surface, said holder being mounted for oscillation to carry said tool endwise into forceful marking engagement with said surface and to lift said tool therefrom on each oscillation cycle; means for oscillating said holder; an actuating member operatively connecting said holder with said oscillation means and being adapted to be oscillated by said means to oscillate said holder; said holder being slidably engaged with said oscillatory actuating member and being relatively movable with respect to said actuating member toward and from the work surface; and means mounted on and carried by said actuating member and being engaged with said holder to establish friction forces causing greater resistance to movements of said actuating member away from the work surface than to movements thereof toward the work surface.

13. In combination, a member adapted to be progressively fed in one direction, an actuating arm adapted to be oscillated through a fixed path of oscillation, said actuating arm being disposed substantially transversely relative to the path of movement of said member, said member being slidably engaged with said arm for movements relative to and substantially transversely of said arm in opposite directions, means for establishing friction forces between said arm and said member for resisting movements of the member relative to the arm in either direction, and said friction force establishing means, arm and member being arranged and constructed to cause said means to establish friction forces of greater magnitude for resisting movements of said member relative to said arm in the direction of feed than the magnitude of the forces established thereby 20 resisting movement of said member relative to said arm in the opposite direction.

14. In mechanism for oscillating a member in a fixed path between predetermined end limits of oscillation and for progressively feeding the member in one direction of the path of oscillation, in combination, a member to be oscillated and fed, said member being mounted for oscillation, an actuating arm adapted to be oscillated through a fixed path of oscillation, said actuating arm being disposed substantially transversely relative to the path of movement of said member, said member being slidably engaged with said arm for movements substantially transversely of and relative to said arm in opposite directions, means establishing friction forces acting on said member for resisting movements of the member relative to the arm in either direction; and said means and said member being constructed and relatively arranged to offer greater resistance to movements of said member in the direction in which the member is to be fed than to movements of the member in the opposite direction.

15. Apparatus for producing indicia markings on a work surface by the mechanical action of an impact marking tool; comprising a holder for the impact marking tool, said holder being adapted to fixedly hold said tool substantially perpendicular to the work surface, said holder being oscillatory to carry said tool endwise into forceful marking engagement with the work surface and to lift said tool therefrom on each oscillation; means for oscillating said holder including a holder actuating connection, said holder being relatively movable with respect to said connection toward and from the work surface; means between said connection and said holder adapted to resist movements of the holder relative to said connection in directions toward and from the work surface; said means being constructed to offer a sufficient degree of resistance to movement of said holder away from the work surface during oscillation thereof toward the work surface to cause the marking tool to forcefully strike against the work surface; and said means being so constructed and arranged as to resist with a lesser degree of resistance movements of said holder in a direction toward the work surface during oscillation thereof in a direction away from the work surface, than the degree of resistance offered by said means to movement of the holder away from the work surface.

THEODORE MILLER.

REFEBENCES CI'EED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 186,234 Dexter Jan. 16, 1877 196,747 Edison Nov. 6, 1877 1,471,869 Turner Oct. 23, 1923 2,117,880 Goddard May 17, 1938 2,337,341 Miller Dec. 21, 1943 FOREIGN PATENTS Number Country Date 304,575 Great Britain Jan. 24, 1929 

